The present disclosure relates to a magnetoresistance effect device using a magnetoresistance effect element.
In recent years, the speed of wireless communication has increased as mobile communication terminals such as cellular phones have become more sophisticated. Since the communication speed is proportional to the bandwidth of the frequency used, the frequency band required for communication has increased, and along with this, the number of high-frequency filters required for mobile communication terminals has also increased. Research on the field of spintronics, which is expected to be applied to new parts for use with high frequencies, has been actively conducted. One of the phenomena attracting attention regarding this is a spin torque resonance phenomenon of a magnetoresistance effect element (see e.g., Nature, Vol. 438, No. 7066, pp. 339-342, 17 Nov. 2005).
For example, by applying a static magnetic field to a magnetoresistance effect element using a magnetic field applying unit while causing an alternating current to flow through the magnetoresistance effect element, ferromagnetic resonance can be caused in the magnetization of a magnetization free layer included in the magnetoresistance effect element, and the resistance of the magnetoresistance effect element oscillates periodically at a frequency corresponding to the ferromagnetic resonance frequency. The resistance of the magnetoresistance effect element also oscillates likewise when applying a high-frequency magnetic field to the magnetization free layer of the magnetoresistance effect element. The ferromagnetic resonance frequency varies depending on the strength of the static magnetic field applied to the magnetoresistance effect element and is generally included in a high-frequency band of several to several tens of GHz.
A Patent Document discloses a technique of changing the ferromagnetic resonance frequency by changing the strength of a static magnetic field applied to a magnetoresistance effect element and suggests a device such as a high-frequency filter using this technique (see e.g., Japanese Unexamined Patent Application, First Publication No. 2017-153066).
The Patent Document discloses that a high-frequency current flows through a high-frequency signal line and a high-frequency magnetic field generated from the high-frequency signal line is applied to a magnetoresistance effect element. However, in the configuration of the high-frequency signal line disclosed, the strength of the high-frequency magnetic field applied to the magnetoresistance effect element may be insufficient.
FIG. 1A and FIG. 1B are cross-sectional view schematically showing a configuration in the vicinity of a magnetoresistance effect element.
A magnetoresistance effect device 10 shown in FIG. 1A includes a magnetoresistance effect element 101 (MR element), a high-frequency signal line 3, a first electrode wiring 7, and a second electrode wiring 8. A magnetoresistance effect element 101 includes a first ferromagnetic layer 101A, a second ferromagnetic layer 101B and a spacer layer 101C (such as a nonmagnetic layer). The first ferromagnetic layer 101A, the second ferromagnetic layer 101B and the spacer layer 101C are stacked such that the spacer layer 101C is disposed between the first ferromagnetic layer 101A and the second ferromagnetic layer 101B. The arrow with a reference numeral L indicates a direction in which such layers are stacked.
Here, the first electrode wiring 107 and the second electrode wiring 108 are lines provided at an upper end and a lower end of an element in order to apply a current or a voltage to a magnetoresistance effect element or to transmit a signal output from a magnetoresistance effect element (electrodes may be provided at an upper end and a lower end of a magnetoresistance effect element in order to increase conductivity and the like, and the line including the electrodes will be referred to as an “electrode wiring” below).
A dotted line X0 in the high-frequency signal line 3 indicates a center line of the high-frequency signal line 3 in a stacking direction of the magnetoresistance effect element 101. The center line refers to a line bisecting the high-frequency signal line 3 in the stacking direction (that is, the thickness direction).
One reason for the strength of a high-frequency magnetic field applied to a magnetoresistance effect element being insufficient is that a distance D0 between the magnetoresistance effect element 101 and the center line X0 in the high-frequency signal line 3 in the stacking direction is large.
Here, in order to increase the high-frequency magnetic field applied to the magnetoresistance effect element 101, as shown in FIG. 1B, the high-frequency signal line 3 is formed to be thinner, and thus the distance D0 between the magnetoresistance effect element 101 and the center line X0 in the high-frequency signal line 3 in the stacking direction is suitably shortened. However, since the electrical resistance (hereinafter simply referred to as “resistance”) is inversely proportional to a cross-sectional area, when the high-frequency signal line 3 is made thinner, the resistance of the high-frequency signal line 3 becomes larger and high-frequency characteristics deteriorate.
It is desirable to provide a magnetoresistance effect device through which it is possible to increase the strength of a magnetic field applied to a magnetoresistance effect element and also reduce the resistance of a high-frequency signal line.